Retaining catalyst fines in fluid hydroforming



RETAINING CATALYST FINES IN FLUID HYDROFORMING Filed March 29, 1957 9E596mm? Kenneth Earl Draeger Inventors ALloyd Arthur Nicolai BY AttorneyUnited States Patent() RETAINING CATALYST FINES IN FLUID HYDROFORMINGApplication March 29, 1957, Serial No. 649,480

' 12 Claims. (Cl. 208-150) This invention pertains to the catalyticconversion of hydrocarbons and particularly to an improved process forthe recovery of catalyst particlesentrained with vaporous reactionproducts from a hydrocarbon conversion reactor operating in accordancewith the uidized solids technique. By the invention catalyst fines inthe reactor overhead which pass the reactor cyclones are concentrated inthe minimum operable amount of polymer and this slurry is returned tothe vupper part of the spent catalyst stripper. Q

'I'his invention will be described hereinbelow as applied to a uidhydroforming operation. It will be understood, however, that it isequally applicable to fluid catalytic cracking or other hydrocarbonconversion operations employing the fluidized solids technique.

Hydroforming is a Well known and widely used process for treatinghydrocarbon fractions boiling within the motor fuel or naphtha range toupgrade the same or increase the aromaticity and improve the antiknockcharacteristics of said hydrocarbon fractions. By hydroforming isordinarily meant an operation conducted ut elevated temperatures andpressures in the presence of solid catalyst particles and hydrogenwhereby the hydrocarbon fraction is increased in aromaticity and inwhich operation there is no net consumption of hydrogen. Hydroformingoperations are usually carried out in the presence of hydrogen orhydrogen-rich recycle gas at temperatures of 750-1150 F. in the pressurerange of about 50-3000 lbs. per sq. inch and in contact with suchcatalysts as molybdenum oxide, chromium oxide, or, in general, oxides orsulfides of metals of groups IV, V, VI, VII and VIII of the periodicsystem of elements alone or generally supportedon a base or spacingagent such as alumina gel, precipitated alumina or zinc aluminates'pinel. A good hydroforming catalyst is one containing about 10 wt.percent molybdenum oxide upon an aluminum oxide base prepared by heattreating a hydrated aluminum-oxide or upon a zinc aluminate spinel.

Fluid hydroforming is a process in which naphtha vapors are passedcontinuously through a dense, fluidized bed of hydroforming catalystparticles in a reaction zone and in which spent catalyst is withdrawnfrom the dense bed and passed to a separate regeneration zone whereinactivating carbonaceous deposits are removed. The regenerated catalystis then returned to the main reaction vessel. Fluid hydroforming hasseveral fundamental advantages over xed bed hydroforming such as (l) theoperations are continuous, (2) the vessels and equipment can be designedfor single rather than dual functions, (3) the reactor temperature isconstant and simulates isothermal fixed bed operations, and (4) theregeneration or reconditioning of the catalyst may be readilycontrolled.

In the conduct of hydrocarbon conversion operations wherein hydrocarbonvapors are passed through a dense, fluidized, liquid-simulating bed oflinely divided catalyst particles, small amounts of vcatalyst particlesbecome entrained in the vaporous reaction products and even after icepassage through cyclone separators or the like which remove the majorproportion of the entrained catalyst particles, small residual amountsof catalyst having a particle size smaller than about l0 microns remainin the product vapor stream. It is desirable for the eco-v nomicaloperation of this process to recover this residual catalyst from theproduct vapors.

In addition it has been determined that it is highly desirable tomaintain a significant proportion of fines in the catalyst fluid bed 'inorder to obtain high catalyst eciency. When catalyst fines passing thereactor and regenerator cyclones are not returned to the unit, thepercentage of coarser catalyst particles increases as does the densityof the lluid bed. It is known that this pro duces a decreasedl catalystutilization. It has been proposed in U.S. Patent 2,663,676 to recoverthis catalyst by.

' quenching or partially condensing the product vapors Y and thus do notproducethe high coke deposition env countered when such fines areintroduced with the fresh f trated diagrammatically. The feed stock,preheated to' feed to the bottom of the reactor. ever,v fines thusreturned to .the reactor tend to be promptly entrained inthe productvapors rather thanv intermixed with the catalyst dense bed.

According to therpresent invention it has been foundthat an improvedsystem results when the fines concenf,

trated in the minimum amount of polymer -are returned to the upper partof the reactor catalyst Withdrawalv This stripper is operated at arelatively lowl stripper. velocity (about 0.5 ft./sec.) and essentiallyall the fines pass down the stripper, are fully stripped by passingthe'` full length of such column, and are then passed to theregenerator. Thus recirculation of catalyst fines between the linesrecovery system and the reactor disperse phase is avoided. By thepresent process the nes are returnedr after regeneration to the lowerpart of the reactor fluidA bed and thus contribute to the fullest tomaintaining the, desired lines content in such iuid bed. Additionally,anV I attriter may be locatedrnear the bottom of the reactor. catalystwithdrawal stripper to increase fines content ifdesired. This attritercan be supplied with ordinary stripping gas, i.e., steam can be used at600 p.s.i.g. Since; fine catalyst of less than 40 micron size is moreexpensive..

to prepare than coarser catalyst, fresh catalyst is often supplieddeficient in rines. The attriter can thus be used to bring the catalystin the system to the proper fines.

content.

Another advantage of returning catalyst fines recovered from the reactoroverhead to the stripper rather than to the reactor disperse phase isthat the catalyst particles which are too small to economicallyrberetained in the, system can be allowed to pass out through the cyclonesin the regenerator. VPrevious systems did not pass these tines to theregenerator at all and the slurry recovery from the reactor caughtextremely line and fine particles more or less indiscriminately. i f

This invention will be more fully understoodby referf ence to theaccompanying drawing in `which the lines recovery andcontrol system forhydroforming is illussubstantially reaction temperature is passedthrough line 1 to distribution nozzles arranged Vat or just abovedistribution grid- 2 near the bottom of reactor vessel 3.

This feed stock may b e a virgin naphth'a, a cracked naphtha, aFischer-Tropsch naphtha or the like. -Wlieu'r Unfortunately, how,

used for catalytic cracking, the feed stock would be a gas oil orsimilar high boiling feed stock.

The reactor 3 is charged with a mass of linely divided catalystparticles fluidized above grid 2, and having an upper level 4. A streamof hot hydrogen-containing recycle gas is supplied from the recyclegas-naphtha separation system, not shown, to line 5. Hot regeneratedcatalyst is added to this stream of gas from line 6 through valve 7 andthe combined stream is passed to the bottom of reactor 3 below bailleplate 2. In some cases it may be desirable to recycle regeneratedcatalyst to the reactor dense bed without pretreatment or withoutpartial reduction from the completely oxidized condition achieved in theregenerator. In this case, care is taken to avoid contact of the hotregenerated catalyst with hydrogen or other reducing gas in the transferline between the regenerator and reactor as by using only steam or inertgas such as nitrogen as the stripping and'conveying gas. Also, ifdesired, a stream of reactor catalyst may be supplied to the regeneratedcatalyst transfer line to cool or control the temperature of thecatalyst undergoing partial reduction or pretreatment.

' Reaction products are taken overhead through cyclone separator orseparators 8 or the like which remove most but not all of the entrainedcatalyst particles. The reaction products are then passed through line 9to product recovery equipment. This equipment is well known in the artand not a part of this invention and so only the catalyst fines recoverysystem will be shown. In scrubber 10 a partial quench is utilized tocondense only the heavy polymer and with such polymer droplets thecatalyst lines. The slurry formed is then passed through line 11 to pump12. This pump pressurizes the liquid so that it may be passed throughline 13 to slurry settler 14 and from there through line 15, cooler 16and line 17 back to spray nozzles in the scrubber 10. The ternperatureand amount of this quench oil are controlled so as to cool the reactionproduct vapors to just below the condensation point of the heavypolymers formed in the hydroforming reaction vessel. The uncondensedreaction products are passed to recycle gas separation and productspurication equipment through line 18.

From slurry settler 14 the concentrated slurry is passed through line 19to slurry recycle pump 20 and thence through line 21 to the upper partof catalyst withdrawal stripper 22. Stripping gas is introduced throughline 23 at a uidization rate lower than that in the main uid bed in thereactor. Thus the nes so introduced will pass down the withdrawalstripper with the catalyst stream passing from the main bed throughwithdrawal port 24. This stripper column is open at the top, andstripping gases pass directly into the disperse phase region of thereactor. If desired, an attriter 25 supplied with steam through line 23can be installed to reduce catalyst particle size on the streamdescending in the stripper. In this case, the stripping steam is alsoused for catalyst attrition. This attriter may be of any of the wellknown types, supersonic, Venturi type, or ejector.

From the bottom of stripper 22 stripped catalyst passes through line 27and valve 28, to regeneration air line 29 through which it passes intothe bottom of regenerator 30. A lluid bed of catalyst is maintainedabove battle plate 31 having an upper level 32. From thc regeneratorregeneration gases pass through cyclone separators 33 to heat exchangemeans. Uneconomically small fines are intentionally allowed to pass fromthe system through cyclones which have been chosen so as to return thedesired size nes only to the regenerator dense bed. From the bottom ofthe regenerator regeneratedv catalyst is passed through line 6 and valve7 back to the recycle gas line for transfer tothe reactor as previouslydescribed.

In order to more fully explain the invention, the following example isset forth with the understanding that it is merely illustrative of theinvention and that the inclusion of 2.0 wt. percent silica thereon.

invention is not restricted to the specific details enumerated therein.

Example A F. to 350 F. boiling range virgin naphtha is hydroformed to 97Research Clear octane number. The catalyst comprises 10 wt. percentmolybdic oxide supported on an activated alumina support stabilized bythe Reactor pressure is 200 p.s.i., recycle gas rate is 5000 s.c.f./b.,and the temperature of the catalyst uid bed is 940 F. Space velocity ofthe naphtha feed is 0.30 pound of oil per pound of catalyst in thereactor and catalyst circulation to the regenerator is 1.0 pound ofcatalyst per pound of oil. The regenerator is operated at a temperatureof 1100o F. and a pressure of 200 p.s.i.g. Catalyst fines recovery fromthe hydroformer reaction products is 0.001 lb. per lb. of oil suppliedto the reactor. These fines concentrated to 0.24 lb./ gal. which areintroduced to the withdrawal stripper lower the temperature in suchstripper 20 F. below the temperature of the main catalyst bed in thereactor and increase the velocity of steam in the stripper by 0.04ft./sec. The velocity of the steam stripping gases is 0.5 ft./sec. andof the vapors through the main hydroformer catalyst bed is 0.9 ft./sec.The attriter operates on 600 p.s.i.g. steam to maintain an 8 to 15 wt.percent concentration of fines 0-40 microns in size.

It is to be understood that this invention is not limited to thespecific example above which has been offered merely as an illustration,and that modifications may be made without departing from the spirit ofthis invention.

What is claimed is:

1. In a process for the conversion of hydrocarbons in Contact with nelydivided catalyst particles in accordance with the fluidized solidstechnique wherein hydrocarbon feed stock is contacted with a dense,fluidized bed of catalyst particles in the lower portion of theconversion zone and in which a stream of catalyst is withdrawn from thedense lluidized bed through a stripping zone for circulation to theregenerator the improvement which comprises withdrawing a stream ofvaporous reaction products containing residual amounts of entrainedcatalyst particles from the top of the conversion zone, partiallycondensing the product vapors to separate the residual catalyst as aslurry in heavy product and recycling the recovered residual catalystslurry to the upper part of the reactor catalyst withdrawal andstripping zone.

2. The process as in claim l in which the velocity of the gases in thecatalyst withdrawal and stripping zone is 0.2 to 1.0 feet/second.

3. In a process for the conversion of hydrocarbons in contact withfinely divided catalyst particles in accordance with the fluidizedsolids technique wherein hydrocarbon feed stock is contacted with adense, tluidized bed of catalyst particles in the lower portion of theconversion zone and in which a stream of catalyst is withdrawn through astripping zone for circulation to the regenerator the improvement whichcomprises withdrawing a stream of vaporous reaction products containingresidual amounts of entrained catalyst particles from the topV of theconversion zone, partially condensing the product vapors to separate theresidual catalyst as a slurry in heavy product, concentrating saidslurry to 0.0i to 1.0 pound'of catalyst per gallon of slurry, andrecycling the concentrated residual catalyst slurry to the upper part ofthe reactor catalyst withdrawal and stripper zone.

4. The process as in claim-3 in which the velocity of the gases in thecatalyst withdrawal and stripping zone is 0.2 to 1.0 ft./second.

5.V The process as in claim 3 in which the velocity of the gases. in thecatalyst withdrawal and stripping zone is 0.2 to,1.0 feet/second and thevelocity of the uidizing gas in the reactor is higher than that instripping zone and is in the range of 0.5 to 2.0 feet/second.

6. In a process for hydroforming hydrocarbon fractions boiling withinthe motor fuel range in contact with nely divided hydroforming catalystparticles in accordance with the iluidized solids technique whereinhydrocarbon feed stock is contacted with a dense, uidized bed ofhydroforming catalyst particles in the lower portion of the hydroformingreaction zone and in which a stream of catalyst is withdrawn from thedense tluidized bed through a stripping zone for circulation to theregenerator, the improvement which comprises withdrawing a stream ofvaporous reaction products containing residual amounts of entrainedcatalyst particles from the top of the conversion zone, partiallycondensing the product vapors to separate the residual catalyst as aslurry in heavy product and recycling the recovered residual catalystslurry to the upper part of the catalyst withdrawal and stripping zone.

7. The process as in claim 6 in which the velocity of the gases in thecatalyst withdrawal and stripping zone is 0.2 to 1.0 feet per second.

8. The process as in claim 6 in which the velocity of the gases in thecatalyst Withdrawal and stripping zone is 0.2 to 1.0 feet/second and thevelocity of the luidizing gas in the reactor is higher than that in thestripping zone and in the range of 0.5 to 2.0 feet/second.

9. In a process for hydroforrning hydrocarbon fractions boiling withinthe motor fuel range in contact with finely divided hydroformingcatalyst particles in accordance with the fluidized solids techniquewherein hydrocarbon feed stock is contacted with a dense, fluidized bedof hydroforming catalyst particles in the lower portion of thehydroforming reaction zone and in which a stream of catalyst iswithdrawn through a stripping zone for `circulation to the regenerator,the improvement which comprises withdrawing a stream of vaporousreaction products containing residual amounts of entrained catalystparticles from the top of the conversion Zone, partially condensing theproduct vapors to separate the residual catalyst as a slurry in heavyproduct, concentrating said slurry to 0.01 to 1.0 pound of catalyst pergallon of slurry, and recycling the concentrated residual catalystslurry to the upper part of the reactor catalyst withdrawal andstripping zone.

l0. The process as in claim 8 in which the velocity of the gases in thecatalyst withdrawal and stripping zone is 0.2 to 1.0 feet/second.

11. The process as in claim 1 in which the vaporous reaction productswithdrawn from the top of the conversion zone contain iine catalyst of aparticle size smaller than about 10 microns.

12. The process as in claim 6 in which the vaporous reaction productswithdrawn from the top of the conversion zone contain ne catalyst of aparticle size smaller than about 10 microns.

References Cited in the le of this patent UNITED STATES PATENTS

1. IN A PROCESS FOR THE CONVERSION OF HYDROCARBONS IN CONTACT WITHFINELY DIVIDED CATALYST PARTICLES IN ACCORDANCE WITH THE FLUIDIZEDSOLIDS TECHNIQUE WHEREIN HYDROCARBON FEED STOCK IS CONTACTED WITH ADENSE, FLUIDIZED BED OF CATALYST PARTICLES IN THE LOWER PORTION OF THECONVERSION ZONE AND IN WHICH A STREAM OF CATALYST IS WITHDRAWN FROM THEDENSE FLUIDIZED BED THROUGH A STRIPPING ZONE FOR CIRCULATION TO THEREGENRATOR THE IMPROVEMEMENT WHICH COMPRISES WITHDRAWING A STREAM OFVAPOROUS REACTION PRODUCTS CONTAINING RESIDUAL AMOUNTS OF ENTRAINEDCATALYST PARTICLES FROM THE TOP OF THE CONVERSION ZONE, PARTIALLYCONDENSING THE PRODUCT VAPORS TO SEPARATE THE RESIDUAL CATALYST AS ASLURRY IN HEAVY PRODUCT AND RECYCLING THE RECOVERED RESIDUAL CATALYSTSLURRY TO THE UPPER PART OF THE REACTOR CATALYST WITHDRAWAL ANDSTRIPPING ZONE.